ELECTRICAL DOUBLE-LAYER INTERACTION BETWEEN HETEROGENEOUSLY CHARGED COLLOIDAL PARTICLES - A SUPERPOSITION FORMULATION

The superposition formula for the electrical double-layer interaction between two uniformly charged spherical particles immersed in an unbou nded electrolyte has been used extensively since its formulation some 50 years ago. However, the corresponding result for two heterogeneousl y charged spherical particles has to date remained elusive. In this pa per, we present such analytical results and also consider the special case of a heterogeneously charged spherical particle interacting with a uniformly charged plate. In the sphere-plate case we suggest a simpl e modification to the superposition result, based on the incorporation of image. effects, that can dramatically improve its regime of validi ty. We assess the validity and accuracy of the superposition formulae by comparison with results of a rigorous boundary element calculation of the electrostatic interaction. (C) 1998 Academic Press.